How to Manage Aphids and Slugs

Eliminate them, or find ways to live together without bugging each other


The slug is a soft-bodied mollusk rather than an insect. Its clump-like body moves along on its foot, and it secretes an oozing trail when it moves. Unlike the sea mollusk, the slug does not require a shell for protection. Slugs must always stay moist to survive so they love wet, dark areas. They can be found underneath surfaces, hiding in large wood chip mulch or at the base of plants. They are active at night so it can be difficult to know if they are damaging the garden. A quick trap of laying cardboard on the bare ground around the base of plants and turning it over each morning to see if they have accumulated can help. Scraping the slugs off and removing them from your garden can offer control. The trap can be reset until the problem subsides. Other options include the application of diatomaceous earth or crushed oyster shells around the base of plants. Both damage the soft body of the slug and will also deter them from entering the area.

Are slugs in your garden? Here are some signs to look for
» Silvery slime trails along the ground or on leaves
» Large ragged holes in leaves
» Scalloped edges on leaves

Organic Treatments
» Diatomaceous Earth: When you see diatomaceous earth it looks just like a ground powder to the naked eye, but when seen under a microscope, you will see two shapes and both are very scratchy to insects with exoskeletons (shells on the outside). These two shapes cut through their exoskeleton and they dehydrate and die. You sprinkle this at the base of plants.
» Dr. Earth Final Stop Yard & Garden Insect Killer: an organic mix of essential oils to control insects
» Beer trap: shallow saucer filled with beer
» Salt: sprinkle slugs with salt
» Copper tape: lay down copper tape near plants affected, will give slugs a shock


Aphids are another nuisance that can wreak havoc in the garden. These true bugs have straw-like mouthparts that they use to pierce and suck the fluids from plant leaves and flowers. Most abundant in spring, they can rapidly reproduce and colonize a plant, with the adult life cycle averaging one month. They favor all sorts of plants and damage them very quickly, but as summer temperatures rise, their population decreases. Aphids love roses, so keep a close eye on your rose bushes. Check just under the rosebuds and under the leaves.

Does your garden have aphids? Here are some signs to look for:
» Wilting and distortion of leaves
» Yellowing and premature death of leaves and plants
» Black sooty mold fungus

Organic Treatments
» Soapy Water: The best way to control them is to use a natural insecticidal soap spray. This solution will control aphids by penetrating their outer layer and drying them out without damaging the plant or beneficial insects which feast on them as well.
» Prune: Remove by hand or prune off affected areas and drop into a bucket of soapy water.
» Repellent Plants: Grow plants that are natural aphid repellents, such as Catnip or Allium
» Grow Aphid trap plants: Zinnias, Dahlias, Asters, Cosmos and Nasturtiums

Benefits of slugs and aphids

Though slugs and aphids may look off-putting, they do offer benefits to the garden that should not be overlooked. Slugs are a food source for toads and birds and also create aeration in soils when tunneling. Aphids are an excellent food source for beneficial insects in the garden such as ladybird beetles and lacewings. They also have an interesting relationship with ants, which will protect them from predators in exchange for the sweet excretion they produce called honeydew.

​These rhythms of nature are in place to control populations and until out of balance, things should be manageable. If environmental factors such as an abnormal abundance of rain occur, both of these populations are likely to increase, but with some natural products and predators and a little extra attention, a gardener can rebalance the wheel with minimal damage to the environment. If we utilize appropriate ways to discourage aphids and slugs, and understand the benefits they provide in our environment, we can find ways to live together without bugging each other.

Visit the Gasper Garden Center and speak to one of our experts about your garden and any challenges you have. We are happy to help!

One minute you’re a slug and the next minute you’re a hero, so you don’t know what to think.

Ed Belfour, Canadian Athlete, hockey